The present invention relates to a probe apparatus for insertion in a patient's mouth and which contains electrical devices for sensing both the patient's temperature and respiration rate.
Due to the recent upsurge in the use of electrical/electronic measuring systems in lieu of the classic means used for sensing various patient vital signs, a need has risen for a simple but efficient sensing probe which may be used repeatedly by a succession of patients. In the past, it has been known to use a combination of sensors each intended to sense a different physiological parameter and all being contained within the same housing. For example, it is known to utilize a temperature sensor, respiration rate sensor and pulse rate sensor all contained within the same housing and which provide the appropriate analog signals to an instrument by the use of suitable connecting cables. The heart of the majority of past temperature and respiration rate sensor systems has been a thermistor which, as is well known, presents a varying electrical resistance in response to variations in temperature. Thermistors have been utilized in the past to provide an indication of the patient's temperature by locating a thermistor in the end of a rod or tube and placing the tube under the patient's tongue. Of course, such thermistor probes may also be used to take the patient's temperature rectally. Similarly, because a person's respiration causes air movement, it is known to detect such air movement by placing a thermistor in the air stream. It is known to heat the thermistor to approximately 50 or 75 degrees Fahrenheit above ambient in still air. Then air motion due to respiration, including the passage of warm expired air, will cool the thermistor, thereby causing cyclic resistance changes coincident with the rate of exhalation. Systems have been disclosed wherein a thermistor is actually located within the nasal passages of a patient. However, more recently temperature sensing probes have been disclosed with a first thermistor located on one end of a rod for insertion into the patient's mouth, and a second thermistor located on the surface of the probe, such that the exhalation from the patient's nose passes over the thermistor and thereby provides the necessary temperature variations. These temperature variations are subsequently used to calculate the respiration rate.
Although such sensing probes have been disclosed and used in the past, they have all been beset by various problems, not the least of which is a bulky design, thereby making it difficult for a patient to comfortably retain the probe in his mouth. Problems have also been found in that when placing a cover over the probe, the operator must use extreme care so as to properly seat the cover on the probe and, more importantly, to properly orient the cover in the patient's mouth so that the respiration sensor is not obstructed or misaligned. A further problem in prior respiration sensing probes has been in locating the thermistor exterior to the housing. In this respect, various designs have been utilized wherein the respiration sensing thermistor sits on a small stalk located midway on the probe body so that the patient's exhalations pass over the thermistor. This design is not only cumbersome but is also vulnerable to damage by rough handling by the operator.